Well I've narrowed it down to 2! Any suggestions or scenarios that might persuade me to get one versus the other?

I've never had a cup. Never even heard of one until I started researching reusable products to minimize waste and maximize the savings. Now that I found them I can't wait to try one! I'm 28, no children but married & active, I think I have a low cervix (or just not much room lengthwise). My flow can be like niagara falls on some days, but I don't know if it's enough to warrant buying a large. Comfort and staying put are my biggest concerns. Any thoughts on why one might be better than the other?